The document discusses the Bionator, a functional appliance developed by Balters in 1956, used for treating malocclusions characterized by mandibular deficiency. It emphasizes the role of tongue positioning and lip seal in orthodontic treatment, detailing the principles of construction and modifications of the Bionator for specific malocclusions. Additionally, the text outlines the advantages, disadvantages, and expected outcomes of using the Bionator in clinical practice.